/* sha1sum.c - print SHA-1 Message-Digest Algorithm
 * Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
 * Copyright (C) 2004 g10 Code GmbH
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*
 * SHA-1 coden take from gnupg 1.3.92.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>

#undef BIG_ENDIAN_HOST
typedef unsigned int u32;
typedef unsigned char u8;

/****************
 * Rotate a 32 bit integer by n bytes
 ****************/
#if defined(__GNUC__) && defined(__i386__)
static inline u32 rol(u32 x, int n) {
    __asm__("roll %%cl,%0"
            :"=r"(x)
            :"0"(x), "c"(n));
    return x;
}
#else
#define rol(x,n) ( ((x) << (n)) | ((x) >> (32-(n))) )
#endif

typedef struct {
    u32  h0, h1, h2, h3, h4;
    u32  nblocks;
    unsigned char buf[64];
    int  count;
} SHA1_CONTEXT;

static void sha1_init(SHA1_CONTEXT *hd) {
    hd->h0 = 0x67452301;
    hd->h1 = 0xefcdab89;
    hd->h2 = 0x98badcfe;
    hd->h3 = 0x10325476;
    hd->h4 = 0xc3d2e1f0;
    hd->nblocks = 0;
    hd->count = 0;
}

/*
 * Transform the message X which consists of 16 32-bit-words
 */
static void transform(SHA1_CONTEXT *hd, unsigned char *data) {
    u32 a, b, c, d, e, tm;
    u32 x[16];

    /* get values from the chaining vars */
    a = hd->h0;
    b = hd->h1;
    c = hd->h2;
    d = hd->h3;
    e = hd->h4;

#ifdef BIG_ENDIAN_HOST
    memcpy(x, data, 64);
#else
    {
        int i;
        unsigned char *p2;

        for (i = 0, p2 = (unsigned char *)x; i < 16; i++, p2 += 4) {
            p2[3] = *data++;
            p2[2] = *data++;
            p2[1] = *data++;
            p2[0] = *data++;
        }
    }
#endif

#define K1  0x5A827999L
#define K2  0x6ED9EBA1L
#define K3  0x8F1BBCDCL
#define K4  0xCA62C1D6L
#define F1(x,y,z)   ( z ^ ( x & ( y ^ z ) ) )
#define F2(x,y,z)   ( x ^ y ^ z )
#define F3(x,y,z)   ( ( x & y ) | ( z & ( x | y ) ) )
#define F4(x,y,z)   ( x ^ y ^ z )

#define M(i) ( tm =   x[i&0x0f] ^ x[(i-14)&0x0f]    \
                      ^ x[(i-8)&0x0f] ^ x[(i-3)&0x0f]      \
                      , (x[i&0x0f] = rol(tm,1)) )

#define R(a,b,c,d,e,f,k,m)  do { e += rol( a, 5 )   \
                                          + f( b, c, d )                          \
                                          + k                                     \
                                          + m;                                    \
    b = rol( b, 30 );                           \
} while(0)

    R(a, b, c, d, e, F1, K1, x[ 0]);
    R(e, a, b, c, d, F1, K1, x[ 1]);
    R(d, e, a, b, c, F1, K1, x[ 2]);
    R(c, d, e, a, b, F1, K1, x[ 3]);
    R(b, c, d, e, a, F1, K1, x[ 4]);
    R(a, b, c, d, e, F1, K1, x[ 5]);
    R(e, a, b, c, d, F1, K1, x[ 6]);
    R(d, e, a, b, c, F1, K1, x[ 7]);
    R(c, d, e, a, b, F1, K1, x[ 8]);
    R(b, c, d, e, a, F1, K1, x[ 9]);
    R(a, b, c, d, e, F1, K1, x[10]);
    R(e, a, b, c, d, F1, K1, x[11]);
    R(d, e, a, b, c, F1, K1, x[12]);
    R(c, d, e, a, b, F1, K1, x[13]);
    R(b, c, d, e, a, F1, K1, x[14]);
    R(a, b, c, d, e, F1, K1, x[15]);
    R(e, a, b, c, d, F1, K1, M(16));
    R(d, e, a, b, c, F1, K1, M(17));
    R(c, d, e, a, b, F1, K1, M(18));
    R(b, c, d, e, a, F1, K1, M(19));
    R(a, b, c, d, e, F2, K2, M(20));
    R(e, a, b, c, d, F2, K2, M(21));
    R(d, e, a, b, c, F2, K2, M(22));
    R(c, d, e, a, b, F2, K2, M(23));
    R(b, c, d, e, a, F2, K2, M(24));
    R(a, b, c, d, e, F2, K2, M(25));
    R(e, a, b, c, d, F2, K2, M(26));
    R(d, e, a, b, c, F2, K2, M(27));
    R(c, d, e, a, b, F2, K2, M(28));
    R(b, c, d, e, a, F2, K2, M(29));
    R(a, b, c, d, e, F2, K2, M(30));
    R(e, a, b, c, d, F2, K2, M(31));
    R(d, e, a, b, c, F2, K2, M(32));
    R(c, d, e, a, b, F2, K2, M(33));
    R(b, c, d, e, a, F2, K2, M(34));
    R(a, b, c, d, e, F2, K2, M(35));
    R(e, a, b, c, d, F2, K2, M(36));
    R(d, e, a, b, c, F2, K2, M(37));
    R(c, d, e, a, b, F2, K2, M(38));
    R(b, c, d, e, a, F2, K2, M(39));
    R(a, b, c, d, e, F3, K3, M(40));
    R(e, a, b, c, d, F3, K3, M(41));
    R(d, e, a, b, c, F3, K3, M(42));
    R(c, d, e, a, b, F3, K3, M(43));
    R(b, c, d, e, a, F3, K3, M(44));
    R(a, b, c, d, e, F3, K3, M(45));
    R(e, a, b, c, d, F3, K3, M(46));
    R(d, e, a, b, c, F3, K3, M(47));
    R(c, d, e, a, b, F3, K3, M(48));
    R(b, c, d, e, a, F3, K3, M(49));
    R(a, b, c, d, e, F3, K3, M(50));
    R(e, a, b, c, d, F3, K3, M(51));
    R(d, e, a, b, c, F3, K3, M(52));
    R(c, d, e, a, b, F3, K3, M(53));
    R(b, c, d, e, a, F3, K3, M(54));
    R(a, b, c, d, e, F3, K3, M(55));
    R(e, a, b, c, d, F3, K3, M(56));
    R(d, e, a, b, c, F3, K3, M(57));
    R(c, d, e, a, b, F3, K3, M(58));
    R(b, c, d, e, a, F3, K3, M(59));
    R(a, b, c, d, e, F4, K4, M(60));
    R(e, a, b, c, d, F4, K4, M(61));
    R(d, e, a, b, c, F4, K4, M(62));
    R(c, d, e, a, b, F4, K4, M(63));
    R(b, c, d, e, a, F4, K4, M(64));
    R(a, b, c, d, e, F4, K4, M(65));
    R(e, a, b, c, d, F4, K4, M(66));
    R(d, e, a, b, c, F4, K4, M(67));
    R(c, d, e, a, b, F4, K4, M(68));
    R(b, c, d, e, a, F4, K4, M(69));
    R(a, b, c, d, e, F4, K4, M(70));
    R(e, a, b, c, d, F4, K4, M(71));
    R(d, e, a, b, c, F4, K4, M(72));
    R(c, d, e, a, b, F4, K4, M(73));
    R(b, c, d, e, a, F4, K4, M(74));
    R(a, b, c, d, e, F4, K4, M(75));
    R(e, a, b, c, d, F4, K4, M(76));
    R(d, e, a, b, c, F4, K4, M(77));
    R(c, d, e, a, b, F4, K4, M(78));
    R(b, c, d, e, a, F4, K4, M(79));

    /* Update chaining vars */
    hd->h0 += a;
    hd->h1 += b;
    hd->h2 += c;
    hd->h3 += d;
    hd->h4 += e;
}

/* Update the message digest with the contents
 * of INBUF with length INLEN.
 */
static void sha1_write(SHA1_CONTEXT *hd, unsigned char *inbuf, size_t inlen) {
    if (hd->count == 64) {  /* flush the buffer */
        transform(hd, hd->buf);
        hd->count = 0;
        hd->nblocks++;
    }

    if (!inbuf)
        return;

    if (hd->count) {
        for (; inlen && hd->count < 64; inlen--)
            hd->buf[hd->count++] = *inbuf++;

        sha1_write(hd, NULL, 0);

        if (!inlen)
            return;
    }

    while (inlen >= 64) {
        transform(hd, inbuf);
        hd->count = 0;
        hd->nblocks++;
        inlen -= 64;
        inbuf += 64;
    }

    for (; inlen && hd->count < 64; inlen--)
        hd->buf[hd->count++] = *inbuf++;
}

/* The routine final terminates the computation and
 * returns the digest.
 * The handle is prepared for a new cycle, but adding bytes to the
 * handle will the destroy the returned buffer.
 * Returns: 20 bytes representing the digest.
 */
static void sha1_final(SHA1_CONTEXT *hd) {
    u32 t, msb, lsb;
    unsigned char *p;

    sha1_write(hd, NULL, 0); /* flush */;

    t = hd->nblocks;
    /* multiply by 64 to make a byte count */
    lsb = t << 6;
    msb = t >> 26;
    /* add the count */
    t = lsb;

    if ((lsb += hd->count) < t)
        msb++;

    /* multiply by 8 to make a bit count */
    t = lsb;
    lsb <<= 3;
    msb <<= 3;
    msb |= t >> 29;

    if (hd->count < 56) {  /* enough room */
        hd->buf[hd->count++] = 0x80; /* pad */

        while (hd->count < 56)
            hd->buf[hd->count++] = 0;  /* pad */
    } else { /* need one extra block */
        hd->buf[hd->count++] = 0x80; /* pad character */

        while (hd->count < 64)
            hd->buf[hd->count++] = 0;

        sha1_write(hd, NULL, 0);  /* flush */;
        memset(hd->buf, 0, 56);  /* fill next block with zeroes */
    }

    /* append the 64 bit count */
    hd->buf[56] = msb >> 24;
    hd->buf[57] = msb >> 16;
    hd->buf[58] = msb >>  8;
    hd->buf[59] = msb       ;
    hd->buf[60] = lsb >> 24;
    hd->buf[61] = lsb >> 16;
    hd->buf[62] = lsb >>  8;
    hd->buf[63] = lsb       ;
    transform(hd, hd->buf);

    p = hd->buf;
#ifdef BIG_ENDIAN_HOST
#define X(a) do { *(u32*)p = hd->h##a ; p += 4; } while(0)
#else /* little endian */
#define X(a) do { *p++ = hd->h##a >> 24; *p++ = hd->h##a >> 16; \
        *p++ = hd->h##a >> 8; *p++ = hd->h##a; } while(0)
#endif
    X(0);
    X(1);
    X(2);
    X(3);
    X(4);
#undef X
}

#define BUFFER_SIZE 4096
static int calc_sha1(const char *filename, size_t calc_size, unsigned char *buf) {
    FILE *fp;
    char buffer[BUFFER_SIZE];
    size_t n;
    SHA1_CONTEXT ctx;
    int read_count = 0;
    int max_read_count = calc_size / BUFFER_SIZE;

    fp = fopen(filename, "rb");

    if (!fp) {
        fprintf(stderr, "can't open `%s': %s\n",
                filename, strerror(errno));
        return -1;
    }

    sha1_init(&ctx);

    while ((n = fread(buffer, 1, sizeof(buffer), fp))) {
        sha1_write(&ctx, (unsigned char *)&buffer[0], n);

        if (read_count++ > max_read_count)
            break;
    }

    if (ferror(fp)) {
        fprintf(stderr, "error reading `%s': %s\n", filename, strerror(errno));
        return -1;
    }

    sha1_final(&ctx);
    fclose(fp);

    memcpy(buf, ctx.buf, 20);

    return 0;
}

/*
 * If a file is greater than 1M, we only calculate the
 * the first 1M part.
 */
int calc_sha1_1M(const char *filename, unsigned char *buf) {
    size_t calc_size = 1 * 1024 * 1024;
    return calc_sha1(filename, calc_size, buf);
}
